This invention relates to air-permeable and waterproof diaper covers.
More particularly, this invention relates to a diaper cover for babies, infants and disabled adults.
In this invention, the term "waterproofing" means the property which prevents the penetration of water by coating and filling the gaps between warps and woofs together with the gaps between fibres of a knitted fabric and forming a continuous film on the knitted fabric. In such waterproof finish, the surface of the knitted fabric is covered to form a wall, and with the exception of a special condition the knitted fabric interrupts the passage of gases and liquids completely. Normally, the finished fabric resists a fair amount of water pressure, however, it has not provided resistance to wetting.
A water proofing and stretching material is a material finished by a synthetic resin as a waterproofing agent.
The term "water repellency" means the property which resists wetting by coating the fibres of a knitted fabric with a hydrophobic material or by directly combining hydrophobic groups to the fibre molecules. Finished clothes retain air permeability together with porosity, but depending on the construction of the clothes and the method of water repellent finishing, the resistance to water pressure changes.
For example, air permeable and stretching material is obtained by coating polyvinyl chloride resin on plain cloth of polyester 100%, 75 denier, 28 gauge, smooth knitting. By JIS L 1079-1976Chemical Fibre Fabric Testing Method, said material showed water pressure resistance exceeding 500 mm (a method based on low water pressure), while the air permeability was zero. But the film shows a good bonding property to plain cloth and has 20% lateral elongation. Thus, the characteristic stretching property of plain knitted cloth is preserved.
Because the polyvinyl chloride resin has some elastic property, even if the plain cloth is elongated, holes are not formed on the surface of the plain cloth thereby damaging the waterproofing property.
The term "air-permeable and water-repellent material" means a material, such as knitted fabric, which is made of synthetic fibres treated by an impregnation of synthetic resin such as of the fluorocarbon type, silicone type or the like to provide water repellency. The material is subjected to heat treatment to retain water-repellency. The treating temperature differs or varies depending on the kind of synthetic fibres. When the material is polyester fibres heat treatment is effected at approximately 170.degree. C., and the result is material having a good feeling and retaining water repellency.
For example, air-permeable and water repellent material is obtained by impregnating a silicone resin liquid on plain cloth of polyester 100%, 100 denir, 24 gauge, smooth knitting, finished weight 260 g/m. This plain cloth is dipped in silicon resin liquid, the resin is deposited on the surfaces of the fibres of said cloth, dried and then finished. In relation to the term "smooth knitting", the two stages of smooth knitting means a doubled form of the rubber knitting by means of both sides of a circular knitting machine, and the three stages smooth knitting means a tripled form of the rubber knitting. By the above mentioned JIS L 1079-1976 Testing Method, said material showed water pressure resistance exceeding 160 mm (a method based on low water pressure method), water repellent degrees exceeding 70 (a method based on spraying method), and air permeable degrees exceeding 20 cc/cm.sup.2 /sec.
The term "air-permeable material" means a cloth, such as a normal knitted fabric, that is not treated for water-repellency or waterproofness. The material has little resistance to water pressure or to passing water therethrough, but provides sufficient air-permeability and stretching properties.
Principally, a diaper cover is required to have water-proofness and air-permeable properties, even though the two properties differs substantially in their functional properties and characteristics. A diaper cover which attaches importance to waterproof properties prevents leakage after urination, but because of the lack of permeability, the diaper cover is liable to become foul or stuffy in the interior thereof. On the other hand, a diaper cover which attaches importance to air-permeability provides for permeation of air and gases and relieves foulness and stuffiness in the interior of the diaper cover, but it is liable to leak urine through the openings used for air permeation.
Accordingly, there has been a need for many years for a diaper cover which has both air-permeability and waterproof properties.